I tried mvindex and split but it doesnt give me a result.
Split and mvindex should work, try this
| makeresults | eval 4G_OutageStart="2020-07-05 22:02:01,2020-07-05 22:02:36,2020-07-05 22:02:58,2020-07-06 03:02:41" | eval 4G_OutageStart=split('4G_OutageStart',",") | eval DataPoints=mvcount('4G_OutageStart') | eval FirstDateTime=mvindex('4G_OutageStart',0,0)
If things are not working, it may be that your data looks like an MV field, but is not. You can check with the mvcount eval statement I included above.