XYZ-Dragon Cannon & Machina Force

This may seem like a dumb question but I haven't played the TCG in years until earlier this week some friends introduced me to this server. I don't really know much about the new #'ed cards from ZeXal and I'm just starting to learn about the Malefic creators and getting the hang of Synchros somewhat. My question lies with something else entirely though.

Question 01:

Say my opponent or I have Imperial Iron Wall activated on the field or some other spell/trap/monster effect which prevents cards from being removed from play.

If a card says 'This card can only be Special Summoned from your Extra Deck by removing from play the above cards on your side of the field. ' such as the XYZ-Dragon Cannon with the effects of Imperial Iron Wall out there does that mean I discard the monsters to the graveyard instead to summon XYZ-Dragon Cannon or does that render the monster unsummonable?

Alright so that first question actually seems like a reasonable question, but this next one is likely to sound stupid...

Question 02:

The card, Commander Covington, must be on the field to use it's effect right? You can't use it from your hand?

If I come up with any more questions that need answers I'll post them.

Thanks for helping!

#1 Yes, Imperial Iron Wall prevents any cards from being removed from play therefore you cannot summon Xyz-Dragon Cannon since you cannot remove its fusion materials from play.

#2 If an Effect Monster does not specify where it should be to activate its effect, it automatically means on the field.

KaousFaustXIII wrote:#1 Yes, Imperial Iron Wall prevents any cards from being removed from play therefore you cannot summon Xyz-Dragon Cannon since you cannot remove its fusion materials from play.

#2 If an Effect Monster does not specify where it should be to activate its effect, it automatically means on the field.

Ah, too bad.

Thanks for helping me with my questions.