This is only half true! The following put option spread (also called vertical put spread) is easily possible in a CashAcct: ShortPut + LongPut But you are right, many other advanced option strategies/constructs are not possible in a cash acct.
Yes, you are correct, but the broker will not treat it as a spread. It will be treated as two separate positions: a long put and a cash-secured short put. So you would have to maintain the cash requirement. Ties up huge amounts of capital when compared to a spread in a margin account.
Hmm. too bad. I think there is no reason for not offering it also in cash acct, after all everything is "covered" in a cash acct, ie. it's more secure than a margin acct, IMO.
Brokers use all kinds of rules and limitations that don't really make sense on a logical or mathematical level. For example, even in a margin account, if you are short stock and long a call, your risk can be very limited. If I short the stock at $50, and buy a 60 call, my max loss is $1000 plus the premium I paid for the call. But the broker won't calculate it that way. It will be two separate positions, and I will have to maintain the margin requirement for short stock, without accounting for the protection offered by the long call. The only way to get past these limitations is to have an institutional account, or maybe a retail account with portfolio margin. But for that you need around $100K in equity.
You are correct. Cannot do spreads in a Cash Account so it is a trade off to a trader's style and needs. Of course you can do it all in a PDT account.
Regarding 4: If that position of yesterday was using only 1/10 of your settled cash, then today you still can do 9 daytrades of same size (ie. each 1/10 of cash of yesterday at mkt close) plus opening another, 10th, position, but as you say must keep the last one overnight. @vanzandt some days ago had posted similar info: