My Dell Inspiron 3501 having 11th gen 1135g7 with igpu iris xe is reaching around 98 degree (aprox for 1 minutes) continiously during video rendering(of 4minutes). After one minute fan kicks on full speed and temperature goes down to around 85. For next 3 minutes temp was around 82-85 degree celcius. Is it safe for my motherboard and CPU????????????? temp graph
Yes. That is within limits and the fact that the Fan kicks in as it should and then the CPU cools down means the Fan is working properly.
So long as it works like this and cools down after a minute means your computer is working properly.
Consider your long term needs as eventually you may need a stronger computer, one geared to high loads. In particular a CPU designed to handle your load over long periods of time on a very good heat sink (the biggest that the manufacturer can fit in).
These temperatures are acceptable, but high.
I don't know much about your hardware and video, but the video codec that you use might not be able to use the GPU. Installing a good codecs pack might help with a better codec that will offload the video work from the CPU to the GPU.
On Windows I recommend the K-Lite Codec Pack.