I believe that there is no certain time when all traders are best able to trade. Everyone should adjust the time to their convenience. You should analyze your efficiency during the day and decide for yourself in what period it is more convenient to trade. As you said there are periods with better liquidity, but if you are not comfortable trading at this time, it is better not to do so, you will lose more than you will get.
Usually London session and New York session are good for trading. In other session you can also trade if you have that kind of strategy. In Tokiyo and Sydney sessions market remains a bit slow. It's the London and New York sessions where market usually are more liquid. Now decision is yours.
The trader has to find the best time of trading for him. It can be different according to your trading style, available time, and investment. For good movement and a volatile market, you should try London and NewYork sessions. If you are not easy at this time you can avail of your free time because when you are easy you will feel now trading is convenient for you.
This is another newbie question and the answer is that there is no right time to trade. The right time to trade is whenever you decide to trade and execute your strategy. While there are time periods with higher liquidity and most of the pros trade the European session it does not mean it is the best time to trade.
It all comes down to the individual, location, preference etc and there is no right or wrong time to trade. Focus on what works for you and stop modeling your trading after the preference of others.
Indeed, moves in the first 15 minutes - 1 hour after London session opening often set market direction for the rest of the day. This indicates that momentum does exist and retail traders can follow it.