AC21 and G-28 filing

[stv]

HI,

1.How soon we need to file AC21 after job change?
2.What is the minimum and maximum period to file AC21 after job change?
3.My wife got EAD and she never used her EAD for work. If I change the job using AC21, do I need to hire a new attorney for AC21 and G-28 filing just for me(Primary) or also for family (Derivative)?
4.Any idea how much it cost to hire an attorney for this?

5. Is it okay with the new job tiitle "Developer" Vs "Senior Application Developer" on PERM?

Please let me now and thank you for your advise