Cascade

[ELLERfeller]

You cast  {Bituminous Blast} and ignore all cards till you reach  {Living End} can you cast it? If you do is it the suspend cost?

[ELLERfeller]

If you exile a card with mana cost less than bthe original cascade spell do you HAVE to cast it?

[rarehuntertay]

For a card with cascade: you cast it, cascade triggers: you reveal until you reveal the first non-land card that costs less than the card with cascade, then cast that card without paying its mana cost.
You don't have to cast the card revealed with cascade.
If you reveal {living end}, you cast it for free as it has a converted mana cost of zero

[Kaylesh]

When you cascade, you reveal cards until you hit a non-land card with mana cost 4 or less (in this case)
You then may cast this card without paying its mana cost.
Since {living end} has a 0 CMC, it qualifies. You may cast it without paying its mana cost, even though that cost was unpayable to start with.
The spell is cast right away.

Even if you'd want to, you cannot suspend it.
Not only because suspend requires the card to be in your hand, but also because suspend is an alternate casting cost, and you can only pay one (without paying its mana cost is also alternate).

EDIT: just as RarehunterTay said about 90 seconds sooner..

EDIT2: regarding your second question, you MAY cast it. If you choose not to, or can't, it goes back in your deck like the other revealed cards.
(Say you hit an X spell, or a {disenchant} that has no valid targets)

[rarehuntertay]

For all your cascade needs: http://mtgsalvation.gamepedia.com/Cascade

[ELLERfeller]

For a card with cascade: you cast it, cascade triggers: you reveal until you reveal the first non-land card that costs less than the card with cascade, then cast that card without paying its mana cost.
If you reveal {living end}, you cast it for free as it has a converted mana cost of zero

but if you come across something with less of a cost before you reach a living end you do have to cast it tho?

[Kaylesh]

For a card with cascade: you cast it, cascade triggers: you reveal until you reveal the first non-land card that costs less than the card with cascade, then cast that card without paying its mana cost.
If you reveal {living end}, you cast it for free as it has a converted mana cost of zero

but if you come across something with less of a cost before you reach a living end you do have to cast it tho?

The first card you hit is the one you can cast. You can't continue until you reach the card you want. Say you hit {doom blade} as first card, that's the one you can cast.

[ELLERfeller]

Okay I get it now! I was cheated at a modern tournament. Wow he skipped the other less cost cards till he reached a living end!

[Kaylesh]

Okay I get it now! I was cheated at a modern tournament. Wow he skipped the other less cost cards till he reached a living end!

General playing tip:
If during a tournament you come across something unfamiliar, take your time. Read the card, if you feel you don't understand it, call a judge.

[ELLERfeller]

Thanks I will make sure of that from now on!