That's not really a detailed enough question to answer you, but here's some generalised stuff...
Jira doesn't have much in the way of SLA tracking built into it, so you'll need to think about how you do it in your organisation and add things to Jira to enable your way of doing it.
You will almost certainly need some coding to support what you want to do, and you'll need to make the call your self about how much you want to do internally, or if it's better to use plugins (free or commercial).
Start by having a look for plugins in the marketplace - a search for SLA will find you some to look through.
However, you've said you are using OnDemand, so you are limited to the ones listed at https://confluence.atlassian.com/display/AOD/Atlassian+OnDemand+Plugin+Policy (none of them directly do SLAs, but some of them will help)
>Closure Expectation Field
That is some form of custom field - I can't tell which type it might be from the description. If it's a standard off-the-shelf custom field, then yes, you can use it in OnDemand. If it's provided by some plugin that isn't in OnDemand, then no.
As with all custom fields, you can associate them with one, some or many issue types, it's entirely up to you.
It does sound like it was a plugin though. You'll need to find out what it was.
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