Based on the fact that one can not be 100% sure of the trend of shares, what is the recommended number of companies that one should buy shares from for the purpose of spreading risk?

What are the risks of buying shares from so many or few companies?

.. with that he should actually put everything in one basket

If you are not sure/Confident, buy 10. If a little confident 6. If very confident, max 3.

Personally i have 10 and only one has displayed -ve returns but is still promising in the long run. However my strategy is buy only and i rarely sell..

Any time you are doing more than 3+ serious stocks in your portfolio you are joining the gamblers group!

Not necessarily, as long as you know how to pick your counters it's not a gamble.It's only gambling if you pick 10 counters with the hope of landing a windfall on some of them.

Have categories, counters that you are to invest in the long term and counters to speculate in. You can identify 4 counters for long term and 1 or 2 counters for speculation.

Everyone expects different things from their investments e.g some invest for the dividends, price appreciation, businesses creating new markets e.t.c Therefore the number of counters one investor buys may not necessarily be what you would want to buy depending on your investment expectations.

My advice, first be sure of what you want from the counters you invest in and then you'll be able to narrow down your choices and come up with a number of counters that works for you.
My two cents

Really? When?