As regards #1, there are a few tricks you can use to exploit the way people play the game without breaking the rules (which you did break the rules, as others have said). If you play a boardwipe, and you see someone else has something else they're very likely to do (for example - they have a skitheryx, the blight dragon sitting around and will probably choose to regenerate it). In that case, you can choose not to cast your indestructible spell. If they activate skittles, priority will come back around to you, but most likely if someone has a counterspell they're planning to use, they'll go ahead and use it rather than wait for skittles regenerate ability to resolve first. So you chance choose to wait until the last minute, once skittles regen ability has resolved and it's the very last time around the board before the boardwipe resolves, and THEN play your indestructible spell.
You can also do this by putting some other, less critical spell/ability of your own on the stack above your board wipe. Like, cast the boardwipe, hold priority, cast heal or whatever. Priority passes for heal to resolve, and then you can cast the indestructible spell once heal resolves.
Now, both of these tricks rely on your opponents not waiting until the last possible chance to cast their counterspells. But they could still theoretically do that. People just usually don't. In the first trick, your opponents could also be super savvy, realize what you're doing, and then choose not to use otherwise-obvious abilities like the skittles one in order to screw you over by not giving you priority back, and just let the board wipe resolve. Or maybe they actually have something else they need the mana for more - it is possible.
Mind you, it's probably not worth it for your deck because you get back the indestructible spell anyway, unless feather's dead, they kill the target in response, or they outright counterspell the indestructible. In your case, it might be cleaner to just cast the indestructible spell BEFORE the board wipe - there's no a lot of reason not to. By putting both on the stack at once, you're just giving your opponents more information.
There, more nitty-gritty than you ever wanted. I told you not to read it.
As regards #1, there are a few tricks you can use to exploit the way people play the game without breaking the rules (which you did break the rules, as others have said). If you play a boardwipe, and you see someone else has something else they're very likely to do (for example - they have a skitheryx, the blight dragon sitting around and will probably choose to regenerate it). In that case, you can choose not to cast your indestructible spell. If they activate skittles, priority will come back around to you, but most likely if someone has a counterspell they're planning to use, they'll go ahead and use it rather than wait for skittles regenerate ability to resolve first. So you chance choose to wait until the last minute, once skittles regen ability has resolved and it's the very last time around the board before the boardwipe resolves, and THEN play your indestructible spell.
You can also do this by putting some other, less critical spell/ability of your own on the stack above your board wipe. Like, cast the boardwipe, hold priority, cast heal or whatever. Priority passes for heal to resolve, and then you can cast the indestructible spell once heal resolves.
Now, both of these tricks rely on your opponents not waiting until the last possible chance to cast their counterspells. But they could still theoretically do that. People just usually don't. In the first trick, your opponents could also be super savvy, realize what you're doing, and then choose not to use otherwise-obvious abilities like the skittles one in order to screw you over by not giving you priority back, and just let the board wipe resolve. Or maybe they actually have something else they need the mana for more - it is possible.
Mind you, it's probably not worth it for your deck because you get back the indestructible spell anyway, unless feather's dead, they kill the target in response, or they outright counterspell the indestructible. In your case, it might be cleaner to just cast the indestructible spell BEFORE the board wipe - there's no a lot of reason not to. By putting both on the stack at once, you're just giving your opponents more information.
There, more nitty-gritty than you ever wanted. I told you not to read it.
EDH Primers
Phelddagrif - Zirilan
EDH
Thrasios+Bruse - Pang - Sasaya - Wydwen - Feather - Rona - Toshiro - Sylvia+Khorvath - Geth - QMarchesa - Firesong - Athreos - Arixmethes - Isperia - Etali - Silas+Sidar - Saskia - Virtus+Gorm - Kynaios - Naban - Aryel - Mizzix - Kazuul - Tymna+Kraum - Sidar+Tymna - Ayli - Gwendlyn - Phelddagrif 4 - Liliana - Kaervek - Phelddagrif 3 - Mairsil - Scarab - Child - Phenax - Shirei - Thada - Depala - Circu - Kytheon - GrenzoHR - Phelddagrif - Reyhan+Kraum - Toshiro - Varolz - Nin - Ojutai - Tasigur - Zedruu - Uril - Edric - Wort - Zurgo - Nahiri - Grenzo - Kozilek - Yisan - Ink-Treader - Yisan - Brago - Sidisi - Toshiro - Alexi - Sygg - Brimaz - Sek'Kuar - Marchesa - Vish Kal - Iroas - Phelddagrif - Ephara - Derevi - Glissa - Wanderer - Saffi - Melek - Xiahou Dun - Lazav - Lin Sivvi - Zirilan - Glissa
PDH - Drake - Graverobber - Izzet GM - Tallowisp - Symbiote Brawl - Feather - Ugin - Jace - Scarab - Angrath - Vraska - Kumena Oathbreaker - Wrenn&6