2. If I cast any pump spell like Giant Growth targeting the Phantasm, are those counted as counters and thus making it able to attack for that turn only?
No. Bonuses from effects like Giant Growth are never counted as counters. Effects that put +1/+1 counters on a creature are explicit about it, they use the term "+1/+1 counter" (note that the term may be contained within a keyword like fabricate or bolster, though). Nothing else will work.
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I'm a lvl 1 judge, but that doesn't make my answers more valid than those of people who aren't judges. What matters is we can quote the rules to back up our answers. When in doubt, ask for such quotes.