2/4 and 3/6 -- Im new to limit-- Contuniation bet/4bet preflop ??

[Percussion]

Lets say hero 2bets in mid position with A [img]/images/graemlins/spade.gif[/img]Q [img]/images/graemlins/heart.gif[/img].
Co raises and then Big Blind 4 bets it and a late position (who limped) cold calls. should I be calling the two extra bets, even though its pretty obvious that I am beat preflop

Second Scenario: lets say I have K [img]/images/graemlins/diamond.gif[/img]Q [img]/images/graemlins/diamond.gif[/img] and I raised from the CO seat and the button, SB, and BB called.
The flop comes down A [img]/images/graemlins/spade.gif[/img] 9 [img]/images/graemlins/heart.gif[/img] 4 [img]/images/graemlins/club.gif[/img]
Giving me just about nothing and it is checked to me. Who checks here, and who bets here? Whats the point of betting (I know to thin the field, but people will call with hands like ATo, K9s