Six disconnect rule in main panel

[Db71]

(1) If I'm running power to a shed from house main panel and have 5 double pole breakers existing can I run a multi wire branch circuit to shed to complie with six handle rule and will this be acceptable means of disconnect without adding one at shed
(2) if panel has six double pole breakers in it is it acceptable/good practice to add suppanel next to main panel and remove one double pole from main to the sub along with other breakers and add double pole feeding sub panel in place where original double pole was in main panel
(3) if main panel has five handles can I add double pole breaker let's say 20 amp (#12)or if shed I'm feeding is let's say 100' away can I add 30 amp double pole (#10)for voltage drop and add subpanel in shed along with breakers to feed Etc. in shed as Long as I don't exceed breaker feeding shed from main panel.
EXAMPLE I have double pole 20 in main panel feeding sub panel in shed and in subpanel in shed I have two single pole breakers feeding shed ( one for a light and few plugs and one for small 110 window a/c for example

 

[Db71]

Multi wire would be 20 amp other wise I would need disconnect at shed is that correct

 

[Db71]

Sorry I also left out that the multi wire branch circuit would be protected by a double pole 20

 

[GoldDigger]

Just to be clear, your main panel does not have a main breaker, and that is why you are keeping handle count to six?
Or are you just out of branch/feeder breaker slots?

 

[Db71]

Main panel does not have main
so a double pole 20 feeding multi wire branch circuit from main would now be the six Handel in the Main panel

 

[ActionDave]

Main panel does not have main
so a double pole 20 feeding multi wire branch circuit from main would now be the six Handel in the Main panel

That is fine.