Q1) What is the nearest tube station to this hotel?
I searched and found the "Novotel London Blackfriars", is that correct?
Except, when I look on their map, that is not in the city, but on the South Bank, nearest tube Southwark (pronounced "suth-uck")
Q2) How to get from Heathrow airport to Southwark tube station?
Look at the tube map here: http://content.tfl.gov.uk/standard-tube-map.pdf
Heathrow (multiple stations) in the lower left, end of the dark blue "Piccadilly Line". Southwark is in square D5/E5, on the grey "Jubillee Line".
1) At Heathrow, go to the tube station for your terminal (follow signs)
2) Buy Oyster Cards (one each), and put some credit on them.
3) Take the dark blue Piccadilly Line to Green Park, then change onto the grey Jubillee Line to Southwark.
4) Then follow the map on the hotel's website.
5) Yes, it is possible for seniors, as long as you can carry or wheel you cases. You will be walking within the tube stations (Green Park and Southwark), and on the surface for a few 100 metres.
6) There is a small place for luggage either side of the doors. Click here for photo. The official luggage space is the grey floor area beside the door. Most people just pile it around their legs, as shown.
The alternative is a pre-booked taxi (known as a "mini-cab" locally). This will be slower and a lot more expensive, but will be door-to-door.