You can file it tomorrow, though if it's under 60 days since entry to the US, you may be asked whether adjusting was your intent from the start...
Not really
Ideally yes, because all I-131 and I-765 take time to get approved.
Of course each case is unique and can take however much it needs to take. You can check processing times here
https://egov.uscis.gov/processing-times/
You can also browse this forum on VJ and check out active monthly thread to see people's reports:
https://www.visajourney.com/forums/forum/138-adjustment-of-status-case-filing-and-progress-reports/
Bear in mind, just like with stock market, any previous performance doesn't predict the future 100%. There's also new administration coming which can affect USCIS prioritites.