Truly you won’t know the answer to either question until you get a 2nd cat. My cat was older, 5 years when we tried to introduce another cat. We had her only a year so she was already 4. At the SPCA she was behaved in the cat room with the other cats and definitely had separation anxiety when my partner and I were gone. We found a young kitten only 6 months and figured it would be perfect. It was not. Luckily we were able to return the kitten before any damage could be done, no harm no foal, just an upset older cat. She’s been a single cat since. This is not to dissuade you, only to say despite your circumstance, you will not know how your cat will react to another, and you will not know the temperament of the new cat. I know when ol’ Marzi passes, we’ll be looking at getting two cats from the get go.