Regarding the attractions – it is not possible.
But regarding the Boat cruise, you actually can enter it multiple times. You will receive 1-day ticket (see http://www.londonpass.com/london-attractions/thames-river-boat-cruise.html) and within those 24 hours, you can use it multiple times. I was there last year, activated the 24-hour ticket in the afternoon and next day morning, it was still valid.
From How does the London Pass work?:
Note: Passes can only be used at each attraction once.
However, as noted by JakubJ, for the Thames boat trip, what you actually get is
Make the most of your London Pass:
- Free 24 hour hop-on, hop-off cruise ticket worth over £18
So for this attraction (alone), you get as many trips as you like, within a single 24 hour period.
So given that the Thames River Cruise is listed as one of the attractions, I’d say the answer is no to both your questions.
Credit:stackoverflow.com‘