Are there any specific field data types which are not available for reporting in salesforce ? Or all fields can be used in reports? Apart from checking manually under setup-> Report Types -> available fields for any specific object , is there any way we can check if some specific fields are available for reporting or not?
All fields on all objects that support reporting can be included in a report. Some fields may have restrictions on which filters may be used (e.g. no filtering allowed, or only equals/not-equals). Note that reports respect field level and record level security, so a field or record may not appear depending on a user's profile settings and/or permission sets. Some "standard reports" also don't include custom fields, but that is a report-specific limitation.