Yes, the main blade (actually all fold-out tools) on the PowerLitre and the PowerPint do lock.
There are notches on the tool blades that lock and can be released.
Can you please explain what you mean when you say "lock outside of the main handles lock"?
The tools lock when fully extended from the main handles.
The joints are screwed, not rivetted. So, yes, you can open the joints and change tools.
I haven't done that, yet.