Trip to Osaka

According to this:http://www.japan-guide.com/e/e2362.html, Im able to use the ticket to travel to Osaka from Tokyo. However according to a Japanese friend of my friend, we can't. So can we or can we not?

Also, what time is the last train to Tokyo? If we miss it, are there any overnight trains? If we take a train to Osaka in the morning and wasn't able to get on the last train back to Tokyo, is it counted as a stamp?

TIA!

With this type of ticket there is no "one train from Tokyo to Osaka" but you can only take slow local trains and the ride between Tokyo and Osaka will take 10 hours and needs 4 to 5 different train transfers. So a one day return travel makes no sense. If you want a fast direct train between Tokyo and Osaka it is the shinkansen what takes 2 hours 30 minutes and costs Yen 27 000 return.

However according to a Japanese friend of my friend, we can't. So can we or can we not?

If you travel during the period of validity of the ticket and have the patience to spend 9 hours on local trains, you can.

Also, what time is the last train to Tokyo?

You will have to leave Osaka by around 3pm in order to make it back to Tokyo before midnight. You will have to transfer trains about five times along the way.