S to C should be tax free. S or C to partnership has tax consequences as the assets are deemed sold at FMV, which would often be a gain if they are fully depreciated.  This would be complicated by any assumption of liabilities in the liquidation as well.

That would potentially be very risky, as both the buyer's and seller's tax returns should agree on the purchase price of the assets.  Not to mention, presumably some of the price is attributable to goodwill. Section 1245 property, in particular has tax ramifications, as tax on the depreciation recapture cannot be deferred in an installment sale, and is due immediately.  Furthermore, the buyer will want to depreciate the assets, and there should be agreement on their purchase price.

Allocating the purchase price among the assets is NOT something that you should be doing.  This is something that is negotiated during sale, between the buyer and the seller.  This information is also reported on Form 8594 and should be included with the tax return. This is something you need to kick back to the taxpayer to solve.  The allocation of the sale price has tax consequences for both the buyer and the seller.

You can "trick" the software by creating one asset with the consolidated totals of the fixed assets - purchase price, depreciation, etc.  An then "sell" that asset, and simply delete all the other assets. Make sure to keep the type of property the same in a consolidated entry.  1245 property is treated differently in a sale than 1250 or 1231 property.

Yes, revoking an S election would make a business a C corp. Filing a partnership election would not change your requirement to liquidate the corporation, with the associated tax consequences.  The IRS would still be looking for a final corp tax return.  The may be circumstances were liquidating a C corp is preferable to liquidating an S corp, but I can't think of any off the top of my head.  

That makes perfect sense as far as the CA Secretary of State is concerned.  However, the IRS will consider this to be an S-corp liquidation.  They will expect a final S-corp tax return with all of the assets and liabilities distributed out at FMV to the shareholders.