#1 Tyler has missed the opportunity. No infraction. Information was gained so reversing decisions (TRP 5.4) doesn't apply
#2 It is clear what Tyler intended to do (see TRP 5.2), so he is considered to have cracked the item. Again, no infraction.
#3 Same as in 3, I believe Tyler proposed a shortcut (TRP 5.2), so he is considered to have cracked the item. No infraction.
#4 see TRP 5.2 and TRP 5.3. As long as the limits stated there apply (i.e. it is not done to cause confusion), it is perfectly reasonable to save time by never placing a counter there. Also read PPG 3.9:
Communication does not need to be verbal. Physical representation such as position in the play-space, or use of markers can be considered communication from that player.