Ann: Trading Halt, page-35

Whenever you sell, you get to 'choose' which of the shares you bought that you are selling.

Ie, if you hold 200 shares and bought 100 of those shares at $20 and 100 at $15,
if you sold 100 today for $12, you could either declare you sold the $20 ones or the $15 ones.

If you pick the $20 ones, you have a $8 loss per share. If you pick the $15 ones, just a $3 loss.

Probably its best to crystallise the greater loss.

The shares you receive from the SPP later can't be sold today, because you haven't received them yet.
Even if you could, by 'picking' those ones to sell you would be up for paying CGT on the gains. Definitely seems better to pick the ones you can sell for a loss.
Even worse, the ones you are receiving from the SPP haven't been held for 12 months yet, meaning you will miss the CGT discount of 50% that applies to shares held for 12 months.

Its probably never best to 'pick' shares for sale that are currently both:
up from your buy price;
and held for under 12 months,
so long as you have other shares that don't meet those criteria to choose from.

The best options will always depend on your own situation and your own reckoning of what you might want to sell in future.

To make sure I have addressed your specific questions:

how do I crystallise losses? Sell some shares that you purchased for a higher price than your sell price
My current holding of LLC is 1.38% below purchase price. do I sell my current holding at a loss to when I bought it? Its your choice whether to sell. If you do sell then you will get a capital loss to offset current or future capital gains taxes.
Or- is there some tax loss specific to a SPP? No, they are treated like any other shares you buy on market.
Are you up for CGT on Sale price-9.80 when you sell you allocation or is it Sale price-Share price on day of allocation? When you sell them it will be the $9.80 purchase price that is used to calculate your gains/losses

This last point means that by exchanging your current shares for SPP ones, when you ultimately decide to sell (important point: you may never) then you will be paying more tax than if you had kept your original ones. But the gains from that exchange today will be higher than net additional tax you might pay when/if you decide to sell in future.