Is it possible to mine a block when others cannot connect my monerod? And is there a difference between others being able connect to my monerod and not being able to connect to my monerod?
You can mine a block and relay it to the network even if others cannot connect to your node, assuming your node can connect to others. You will have fewer connections to the network though, and that means (assuming your internet connection isn't super slow) your block may take longer to propagate through the whole network, which means your block has a higher probability of being orphaned, losing you the block reward.
So it is in your interest to have incoming connections, but it's not a deal breaker.
There are no functional differences between incoming and outgoing connections for the mining point of view. For other things, Dandedelion is the only difference that comes to mind.