onward journey rules

I wanted to understand the telescopic rates for onward journey. I plan to go to Kumbakonam from Mumbai. I plan to take 2163 from Dadar to Chennai Egmore which reaches the next day evening. The same evening I plan to take the rockfort express to Kumbakonam. The gap will be just 2.5-3hrs
To me it seems this does not constitute a break journey. If I book this as an onward journey, will i get the advantage of telescopic rate.
The second question is: One can book tickets 90 days in advance. But the second leg of the journey starts the next day ie 91st day. Will I be allowed onward journey booking on -90 days or shud I wait for an additional day till the 90 days window for teh second leg opens.

Thanks and Regards