JIRA sprint field Id

[Vladimir]

Me and my team works on project, which involves interactions with JIRA via it's REST Api. Now we are a bit confused, as JIRA has system field Sprint, which seems to be immutable in JIRA's admin side, and it seems to be custom, with Id in our JIRA instance "customfield_10100".

- Is JIRA Sprint field custom, and could it be edited in this case ?

- Does it always have Id customfield_10100 in any JIRA instance, or in other JIRA instances these Id-s would/could be different, like customfield_10101 / customfield_10110 / customfield_10201, etc. ?

- If so, what is the algorithm to determine the Id of Sprint field in any JIRA instance using JIRA's REST Api ?

Would be grateful to any valuable response !