Tea tastes better if made in a pot.
The taste of tea as per persived is actually an odour (the biterness of it is a taste). If you make a tea in a pot, pouring it in a cup increases the amount of oxygen in the liquid (a bit like stirring a cocktail) doing so, the quantity of flavouring molecules in the tea reaching the back of the nasal cavity is greater, hence making the tea more “flavoured”. So yes making tea in a tea-pot make some better tasting tea.
Squeezing the bag against the cup makes the tea bitter.
Well that’s easy, polyphenols (or tannin) are the molecules responsible for the bitterness of tea (phenomenon of astringency). Basically, the more you leave tea in a cup of hot water, the more polyphenols you diffuse in the tea. Therefore pressing the bag of tea, will increase the concentration of polyphenols in the tea cup hence making it more bitter.
Any other questions?