Saying 32 bit Mint is more stable than 64 bit Mint is like saying granite is more stable than concrete. Either is miles more stable than Windows of any flavor.
Adobe flash does not come in a 64 bit version yet. They have an alpha testing version available but I haven't tried it.
You are right about 32 bit systems not being able to address more than approximately 3.2 Gb of Ram but for most every day uses, 3 Gb is more than adequate.
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