Should I invest in bitcoin? Yes. Bitcoin as time goes by, continue to increase its demand. More and more people discover bitcoin. Infrastructures around bitcoin continue to increase too. More and more altcoins and companies uses bitcoin for payments for the promotion of their campaign. Should I wait? Yes. In order to get your maximum desired profit, you have to wait/monitor btc value from time to time. The fluctuation of value helps you buy bitcoin in a cheaper price.
No, you must invest more in altcoin, bitcoin unstable and can happen crash any time.
Neo is better

it's correct. Just investing in btc is quite risky. You should watch the alt market and pick out a few alt to invest in it. But I will not say which alt is good for the investment. Because even btc, a major currency in the ctypto system, has existed for a long time and still has not had the confidence of investors, then don't mention alt. if you wanna invest in btc, you must wait.