can I still file single if I married on Oct 26, 2024

No you are married as of Dec 31.  You either file a Joint return or as Married Filing Separately

Getting Married FAQ
https://ttlc.intuit.com/community/tax-filing-status/help/what-does-getting-married-mean-for-my-taxes/00/1756642

Tax info on getting married
https://turbotax.intuit.com/tax-tips/marriage/getting-married/L0DvEUlEC

Did you both use Turbo Tax last year?

You can not transfer from or combine 2 returns or accounts. Just pick the return for the spouse that has the most complicated return to enter or has any depreciation or business or more investments. Or use the account/return for whoever you want to be listed first going forward (by the way you can not change the order of the names). Then add the other spouse's name, ssn and info to it.

But if you want to keep the prior accounts separate from the new Joint account then start a new account. Online is only good for one return per account. But you can use the same email address for 5 accounts.

NO.   Even if you got married at five minutes before midnight on 12-31-24 you are married for 2024.

If you were legally married at the end of 2024 your filing choices are married filing jointly or married filing separately.  Filing Single is not an option.

Married Filing Jointly is usually better, even if one spouse had little or no income. When you file a joint return, you and your spouse will get the married filing jointly standard deduction of $29,200 (+ $1550 for each spouse 65 or older)  for 2024. You are eligible for more credits including education credits, earned income credit, child and dependent care credit, and a larger income limit to receive the child tax credit. 

If you choose to file married filing separately, both spouses have to file the same way—either you both itemize or you both use standard deduction. Your tax rate will be higher than on a joint return.

 Some of the special rules for filing separately include: you cannot get earned income credit, education credits, adoption credits, or deductions for student loan interest. A higher percent of your Social Security benefits may be taxable. Your limit for SALT (state and local taxes and sales tax) will be only $5000 per spouse. In many cases you will not be able to take the child and dependent care credit. The amount you can contribute to a retirement account will be affected. If you live in a community property state, you will be required to provide additional information regarding your spouse’s income. ( Community property states:  AZ, CA, ID, LA, NV, NM, TX, WA, WI)

 If  you are using online TurboTax to prepare your returns, you will need to prepare two separate returns and pay twice since with online, you get one return per fee.

https://turbotax.intuit.com/tax-tips/marriage/should-you-and-your-spouse-file-taxes-jointly-or-separately/L7gyjnqyM?srsltid=AfmBOopGqCNexowW0pYgvsf7ycIkrx4VjO_63UXv6vSnfu3UEGQiKQTh

https://ttlc.intuit.com/turbotax-support/en-us/help-article/income/getting-married-mean-taxes/L2RgmagpE_US_en_US?uid=m69on7t0

https://ttlc.intuit.com/turbotax-support/en-us/help-article/taxation/married-filing-separately-community-property/L11CeLUMs_US_en_US?uid=m69ousyh