Your bill either failed to go through the last printing stage where the seal and serial numbers are added, or it may have accidentally been flipped over and the seal and numbers were printed on the back side. Either way this is considered to be a significant error and could sell in the $300-400 range.
$500.00
Depending on quality it could retail for $100 to $200. This error happens if the sheet of paper on which the bill was printed was accidentally reversed before being fed through the part of the process that adds seals and serial numbers.
One dollar.
Still one dollar....sorry : (
It's still worth one dollar.
If the coin is a US Kennedy half dollar dated 1974 it has no silver in it and is face value.
1974 would make it an Eisenhower dollar, which is only worth face value.
This error is called an "Inverted Overprint" and can retail anywhere from $150 to $400 depending on the bill's condition.
2 dollars
Current retail is $2.40
50 cents
Australian One Dollar notes designated with "AUSTRALIA" were issued from 1974 to 1982. You do not give any useful information like the serial number range or the signatories on the note. If by "sec numbers" you mean "consecutively numbered serial numbers", I assume that they are uncirculated and in mint condition. Depending on the signatories and serial number range, they could be worth up to $85 AUD each, or as little as $7 AUD each. If they are not in mint condition, they are worth at least One Dollar at the very worst. A consecutively numbered range would appeal to certain banknote collectors and possibly have a higher collective value. A reputable coin dealer will be able to give a more accurate valuation.