My fans are acting weird now

Phone freezes, lags, and gets stuck on blue screen.

What's the most updated OS this iMac can go up to?

Would this Harddrive be compatible with my device?

How do I reset to factory settings

How to run diagnostics

Power button creating weird situations

Not sure why the iMac isn't booting

iMac Intel 20" EMC 2133 and 2210 Ambient Temperature Sensor Replacement